Sec. 4. 38 MRSA 420-D, sub-§12 is enacted to read:

12.__Significant existing sources.__The department may require a person owning or operating a significant existing source of storm water to implement a storm water management system.__The owner or operator shall obtain approval from the department pursuant to this subsection for the storm water management system.__The department shall identify significant existing sources as provided in this subsection.

A.__The department shall develop a total maximum daily load for the watershed of a waterbody impaired due to urban runoff prior to designating significant existing sources within the watershed.

B.__The department shall adopt rules prior to requiring that an owner or operator of a significant existing source within the direct watershed of a specific waterbody obtain approval of a storm water management system.__The rules must include provisions requiring the following:

(1)__The name of or other means of identifying the waterbody that is impaired due to urban runoff;

(2)__A list of significant existing sources or a description of the types or classes of significant existing sources;

(3)__A date or schedule indicating when approvals must be obtained; and

(4)__Storm water quantity and quality standards for storm water management systems.

C.__The owner or operator of a site designated as a significant existing source shall apply to the department for approval of a storm water management system.

D.__For purposes of this subsection, a "significant existing source" is a significant source of storm water quantity pollution or quality pollution from a developed area that was in existence prior to July 1, 1997 and is located in the direct watershed of a waterbody that is impaired due to urban runoff.__Significant existing sources do not include: